1. Field of the Invention
The invention relates generally to devices for slip-forming concrete structures, such as divider walls, retaining walls, and other vertically extending barriers. More specifically, the invention pertains to an apparatus including one or more impression rollers, strategically positioned at the discharge end of a slip-form, to impress aesthetic patterns on the sidewalls and on the top wall of the slip-formed structure, just after the structure has been formed and before the concrete has cured.
2. Description of the Prior Art
Concrete walls have long been employed in freeway construction, both as divider walls between opposing directions of traffic, and as retainer walls extending along the sides of the outermost freeway lanes. Concrete walls are also used as barrier walls along property lines, and as aesthetic features in industrial or commercial landscaping. The need for concrete walls also arises to prevent erosion along the periphery of man-made lakes, and along river banks and coast lines.
Historically, concrete forms have been constructed from plywood and restraining posts assembled on the wall site, to shape, size, and direct the wall. After the concrete has been poured into the form and has cured sufficiently, the form is disassembled and another form is constructed for the adjacent wall section. This process is both labor intensive, and slow, owing to the amount of construction and disassembly of forms which it necessitates.
A relatively recent development in the concrete wall construction industry, is the application of a technique known as slip-forming. Instead of constructing a form on site, a mobile slip form is used. The mobile slip form is mounted to the frame of a motorized vehicle. A guide line is laid out defining one edge of the wall to be formed. The frame of the vehicle includes fore and aft alignment rods, maintained in contingent relation with the guide line by the operator.
As the motorized vehicle progresses forwardly down the guide line, fresh concrete is continuously poured into the slip form. The slump and constituent materials of the concrete mix are such that multiple vibrators, immersed within the slip form, are necessary to ensure thorough consolidation of the mix. When the formed concrete emerges from the output, or trailing edge of the form, it has smooth sidewalls and a smooth top wall.
If the slip-formed wall is relatively short, on the order of three to four feet, the entire wall including a spread footer, can be formed without structural reinforcement, in a single pass of the slip-form machine. If the wall is higher, a reinforcement bar cage is typically used in combination with a larger and formed, footer. Although the reinforcement cage must be constructed beforehand, the slip-form concrete pour technique has still been accomplished in a single pass of the slip-form machine, even for a tall wall up to eight feet, or so.
There are a number of commercially available slip-form machines. One such machine is the Commander III, manufactured by the GOMACO Corporation, of Ida Grove, Iowa. This machine has been used successfully to slip-form vertical walls up to 8′8″ high, and to slip-form roadways. At least one paving operation at a dairy farm is known, using the Commander III, in which a free-floating steel roller was used to imprint a cobblestone pattern on the flat surface of the just-formed concrete roadway. The roller included rigid, rib-like protrusions on its outer periphery, corresponding to the cobblestone pattern. The pattern was impressed in the roadway to provide traction for the cattle, to keep their feet from slipping.
However, when slip-forming walls using known prior art machines, the sidewalls and the top wall emerge from the form uniformly smooth, and cure having the same smooth appearance. These walls have been recognized as visually unappealing for certain applications, so surface amendments have been added to the smooth surface. Walls have been colored with stain or paint, or decorative plates have been applied to the smooth walls after the concrete has set. These surface amendments consume additional time and materials, and increase the overall cost of the wall construction.
Therefore, the need exists for an apparatus which slip-forms a wall and concurrently creates a visually appealing pattern or impression in the surface of at least one sidewall of the wall.
The need exists for an apparatus which can be used in conjunction with existing slip-form machines, to impress a visually appealing pattern in the exposed surface of a slip-form wall just after it emerges from the slip form.
The need also exists for an apparatus which slip-forms a wall and concurrently creates patterns or impressions in both surfaces of the sidewalls and in the top wall.
The need also exists for an apparatus which includes an impression roller which is easily and quickly interchangeable with another impression roller, to create a wide variety of different patterns or impressions in a slip-formed wall.
The need further exists for a two-stage impression roller for use with an apparatus manufacturing a slip-formed concrete wall, which concurrently creates patterns or impressions both in the surface of a vertical sidewall portion and in the surface of an angled stem portion of the wall.
Lastly, the need exists for an impression roller for use with an apparatus manufacturing a slip-formed concrete wall, creating a substantially continuous pattern or impression which repeats along the extent of the wall.